Concerted Modification of Flowering Time and Inflorescence Architecture by Ectopic Expression ofTFL1-Like Genes in Maize    

Abstract

TERMINAL FLOWER1 (TFL1)-like genes are highly conserved in plants and are thought to function in the maintenance of meristem indeterminacy. Recently, we described six maize (Zea mays) TFL1-related genes, named ZEA CENTRORADIALIS1 (ZCN1) to ZCN6. To gain insight into their functions, we generated transgenic maize plants overexpressing their respective cDNAs driven by a constitutive promoter. Overall, ectopic expression of the maize TFL1-like genes produced similar phenotypes, including delayed flowering and altered inflorescence architecture. We observed an apparent relationship between the magnitude of the transgenic phenotypes and the degree of homology between the ZCN proteins. ZCN2, -4, and -5 form a monophylogenetic clade, and their overexpression produced the strongest phenotypes. Along with very late flowering, these transgenic plants produced a "bushy" tassel with increased lateral branching and spikelet density compared with nontransgenic siblings. On the other hand, ZCN1, -3, and -6 produced milder effects. Among them, ZCN1 showed moderate effects on flowering time and tassel morphology, whereas ZCN3 and ZCN6 did not change flowering time but still showed effects on tassel morphology. In situ hybridizations of tissue from nontransgenic plants revealed that the expression of all ZCN genes was associated with vascular bundles, but each gene had a specific spatial and temporal pattern. Expression of four ZCN genes localized to the protoxylem, whereas ZCN5 was expressed in the protophloem. Collectively, our findings suggest that ectopic expression of the TFL1-like genes in maize modifies flowering time and inflorescence architecture through maintenance of the indeterminacy of the vegetative and inflorescence meristems.

Transcriptome Profiling of Tiller Buds Provides New Insights into PhyB Regulation of Tillering and Indeterminate Growth in Sorghum

“…4). TFL1's role in preventing floral induction is well known (Lifschitz et al, 2014) and expression of ZCN2 (TFL1/SbCN2) was previously reported in axillary buds of maize (Danilevskaya et al, 2010). Elevated expression of SbCN2 in buds of phyB-1 plants indicates that in the absence of phyB-signaling, increased expression of TFL1 enhances the barrier to floral induction.…”

“…4). ZCN4 is expressed in maize root apical regions (Danilevskaya et al, 2010). The increase in expression of this gene in phyB-1 at 8 DAP may indicate that nascent root meristems of the bud have developed and require protection from premature differentiation.…”

“…Grain sorghum is classified as weakly perennial (Dewet and Huckabay, 1967), but sorghum germplasm can exhibit a wide range of annual to perennial growth habits. Sorghum and maize florigens are produced in leaves by ZCN8/ SbCN8 and ZCN12/SbCN12 (Danilevskaya et al, 2010;Murphy et al, 2011). Flowering in sorghum is inhibited in long day photoperiods by repressing the expression of SbCN8 and SbCN12 through a pathway that requires phyB-signaling (Murphy et al, 2011;Yang et al, 2014).…”

“…TFL1 is expressed in the shoot apical meristem and axillary meristems of Arabidopsis (Conti and Bradley, 2007), maize (Danilevskaya et al, 2010), and sorghum. The proposed function of Elevated expression of the TFL1-like gene SbCN2 in phyB-1 sorghum tiller buds is to protect these vegetative axillary meristems from florigenic signals in a manner similar to perennial plants.…”

Development of Near Isogenic Lines of Wheat Carrying Different Spike Branching Genes and Their Agronomic and Spike Characters

“…In addition, the new type of spike morphology, branched spike, was produced from the interaction of sb1 and sb2. This kind of branched inflorescence generally was produced from ectopic SAM (shoot apical meristem) (Danilevskaya et al, 2010)，and sb1 and sb2 might be synergistically involved in the formation of ectopic SAM in wheat young spike. The distinct roles of sb1 or sb2 and their combined roles also deserve to be studied more deeply.…”